Microphone for high-tension currents.



. Patented Oct. 28, 902.

a. GAILLA'BD & E. DUCBETET. mcnoPnomz FOR man msmu cunneursa (Applibation filed maria-1902.

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UNTTED STATES RAOUL GAILLARD AND EUGENE PATENT QFFTCE.

DUCRETET, on PARIS, FRANCE.

SPECIFICATION forming part of Letters Patent No. 712,056, dated October 28, 1902.

Application filed March 3,1902.

To all whom it may concern: Be it known that we, RAOUL GAILLARD and EUGENE DU ORETET,citizens of the French Republic, and residents of Paris, France, have invented certain new and useful Improvements in Microphones for High-Tension Currents, of which the following is a specification.

Our invention relates to improvements in microphones for use with high-tension currents, whereby the microphone portion, properly speaking, is arranged in such a manner as to provide for extensive division of the microphone-grains and a more perfect function of the microphone in its entirety. We attain these objects by means of the improved construction of microphone and its separate parts illustrated in the accompanying drawings, in which- Figure 1 is a central section through a microphone embodying ourinvention, taken on line 1 1 of Fig. 3. Fig. 2 isa like section at right angles to the foregoing, taken on line 2 2 of Fig. 3; and Fig. 3 is a top plan view with the membrane or diaphragm removed.

In the drawings the letter P denotes a disk of conducting material, preferably metal, having its internal operative surface faced with any appropriate inoxidizable metal. The internal surface of the disk is striated and is, moreover, divided into any conven-. ient number of compartments S S S S S, sepa: rated from each other by means of narrow strips 8 of flexible material or light fabric cemented in grooves 5, formed in the disk P on the striated side. (See Figs. 1 and 3.)

T is a ring of soft velvety fabricsuch as felt, Pyrenees fabric, or other similar materialcemented upon a ring and then upon the disk P. The strips of said fabric reach as far as or are in direct contact with said ring T, so as to render the compartments S S S S S independent of each other.

The vibrating membrane m is made of conducting material, advantageously hard carbon. Said membrane m is seated upon an insulating-frame E, upon which it is retained by a metallic ring or mounting b and a number of suitable spring-clips WW" 1". I The membrane is so regulated beforehand as to come in contact with the soft ring T and also in contact with every one of the flexible strips Serial No. 96,725. (No model.)-

ihereinbefore mentioned as forming the partitions of the microphone-compartments S S S S S. The various compartments thus separated from one another and formed with striated floor are charged with microphone-grains b or variable resistance consisting of granulated graphite or carbon of convenient size for use in the microphone. Said grains are loosely filled in without stamping down, so as to reachup to the membrane m. The latter by reason of the vibrations imparted to it produces endless variations of microphonic pressure, whereby m and P form conductors for the current which passes through the grains placed at c. The said cond noting-grains cannot change from one compartment S to another. Now this particular arrangement insures the proper function or action of the microphone even if it operates several telephones used by loud-voiced speakers requiring a certain current.

The improved microphone is adapted for general use'in connection with telephonic installations and may be combined singly or in numbers with induction or transformer coils and also with condensers, whereby the grouping and the capacity, which is adjustable, depends on the results to be attained for telephone-stations with or without wires.

Any suitable holder may be employed for the microphone.

We do not claim, broadly, the application in telephonic microphones of flexible material; but

What We do claim as our invention, and desire to secure by Letters Patent of the United States, is

1. In a microphone, the combination with a striated conducting-plate, a ring of soft velvety material mounted upon said plate and a vibrating membrane placed above said ring, of strips of flexible material dividing the space between said plate and membraneinto anumber of independent compartments, and a variable resistance 0 of granulated material filling said compartments as herein stated. I

2. Inamicrophonecomprisingastriatedinner conducting-plate, a ring of soft velvety material and a vibrating membrane and strips of flexible fabric forming compartments between said plate and membrane, the outer frame carrying both the plate and membrane ternal flanged ring the spring-clips for firmly and fitted with an external flanged metal securing said parts together, as stated.

ring, as and for the purpose stated. 3. In a microphone comprising an inner I 5 striated plate, a ring of soft fabric, a number J A of flexible strips of fabric forming colnpart- \Vitnesses: ments, a vibrating membrane, a frame carry- I J. ALLISON BOWEN, ing both said plate and membrane, and an ex- I EDWARD P. MACLEAN. 

